16srDNA
An aliquot of 100 mg (wet weight) of each fecal sample was extracted by a bead-beating method using the ZR Fecal DNA KitTM (Zymo Research Corporation, Irvine, CA) following the manufacturer's instructions. The bead-beating step was performed on a homogenizer (FastPrep-24, MP Biomedicals, Santa Ana, CA) for 60 seconds at a speed of 4 m/s. The fecal DNA was stored at -80C until analysis. After extracting total DNA from the samples, primers were designed according to the V3-V4 hypervariable region of the bacterial 16S rRNA gene. Then sequencing adapters were added to the ends of primers. The target sequences were amplified by PCR, and their products were purified, quantified, and homogenized to get a sequencing library. Library QC was performed for constructing libraries. Qualified libraries were sequenced on the Illumina Novaseq 6000.